The present invention relates generally to methods of making laminated film articles, apparatus for making laminated film articles, and more particularly, to apparatus and methods for making laminated film articles having inflatable chambers and channels.
Conventional cushion materials include thermoformed sealed laminate articles such as Bubble Wrap(copyright) cushioning material. However, it is also known to prepare laminated inflatable articles which can be shipped to a packer uninflated, and inflated immediately before use. Such inflatable articles are typically made from two heat sealable films which are fused together in discrete areas to form one or more inflatable chambers.
Conventional methods of making cushion material, such as Bubble Wrap(copyright) cushioning material, use a vacuum source to deform polymer film to form bubbles or pockets that can be filled with air (or other gases) to form bubbles. Such products can be made using a heated drum having recesses that are connected to a vacuum source. When vacuum is applied, each of various regions of the heated film in contact with the drum is drawn into a recesses on the drum. The heated film is deformed and thinned in the regions drawn into the recess by the vacuum process. One side of the resulting film remains xe2x80x9cflatxe2x80x9d, while the other side is not flat, but rather is xe2x80x9cthermoformedxe2x80x9d. A second film, which preferably is a flat film, i.e., not thermoformed, is fused to the xe2x80x9cflat sidexe2x80x9d of the formed film, resulting in a plurality of sealed, air-filled xe2x80x9cbubbles.xe2x80x9d
Conventional cushion fabricating processes also include a first stage film fabrication step and a separate second stage fusing step. In the first stage, polymer films are fabricated by conventional techniques known to those in the art of polymer film fabrication. In the second stage, the polymer films are combined according to heat sealing methods that are known to those in the art of polymer film sealing techniques.
Two-stage manufacturing processes are undesirable because of the added cost and inefficiency associated with the process. During two stage processes, films are fabricated and wound onto rolls at one location, and unwound and combined with a second film to make a cushioning material at a second location. The processes are inefficient in that they include winding and unwinding of rolls of film, together with inventorying and transporting, as well as other inefficiencies associated with two-stage processes.
The present invention overcomes the inefficiencies and other detriments described above with an integrated, one-stage process for making an inflatable laminated inflatable article. The process of the invention uses a single stage to go from polymer extrusion to form the film or films, thereafter sealing the film or films together to form inflatable chambers between the films.
As a first aspect, the present invention is directed to an integrated process for making an inflatable laminated article, comprising the steps of: (A) extruding a first film and a second film; (B) cooling the first film and the second film so that the films will not fuse to one another upon contact with each other; (C) contacting the first film with the second film; (D) heating selected portions of at least one of the first and second films to a temperature above a fusion temperature, so that the first and second films are heat sealed to one another at a selected area, with the selected area providing a heat seal pattern in which the unsealed portions between the films provide inflatable chambers between the first film and the second film. Of course, if one or more of the films are multilayer films having a sealing layer, the heating of such film need only be to a temperature above the fusion temperature of at least the seal layer of one or more of the films.
While it is preferred to have the C and D steps in this order, they may be reversed in order, i.e., by first heating selected portions of at least one of the films followed by contacting the first film with the second film so that the first and second films are heat sealed to one another at selected areas. Moreover, the selected areas need not correspond exactly with the selected portions which are heated. That is, the portions which are heat sealed may be slightly larger or slightly smaller than the selected portions which are heated.
While the cooling can be active (e.g., contacting one or more films with one or more chilled rolls, belts, the use of cool air or water, etc.), it can also be passive, e.g., simply providing the first and second films enough time to cool under ambient conditions so that they do not fuse to one another upon contact. Thereafter, in order to heat seal the films to one another, it is necessary to heat at least the seal layers of one or both of the films to a temperature at or above a temperature at which the one or more of the seal layers will fuse.
Preferably, the first and second films are extruded simultaneously. Although it is possible to extrude both films from the same extruder (followed by separation from one another), preferably the first and second films are extruded using separate extruders. Either or both the first and second films can be extruded using an annular die or a slot die, i.e., as an annular film or as a flat film, respectively. If an annular die is used, the resulting lay-flat tubing can either be self-welded into a flat film, or converted to a flat film by being slit in the machine direction.
Preferably, the contacting of the first film with the second film is carried out by forwarding the first film and second film together at the same speed. Although heating of selected portions of one or more of the films can be carried out before the films contact one another, preferably the heating of the selected portions of the first and second films is carried out while the first and second films are in contact with one another, with the heat sealing being carried out using a combination of heat and pressure. In one embodiment, the contacting step and the heating step are performed simultaneously, with pressure being simultaneous with the heating, resulting in contacting and heat sealing being essentially simultaneous. During sealing, preferably heat and pressure are applied simultaneously.
Preferably, heating is performed by passing the first and second films together through a nip between a first roll and a second roll, with at least one of the rolls having a patterned raised surface and at least one of the pair of rolls being heated. Preferably the patterned roll is heated. However, both the first roll as well as the second roll can be provided with a raised surface, with the raised surfaces being operatively aligned to heat seal the selected portions of the first film and the second film. Preferably, each roll with a raised surface has a continuous raised surface so that the nip between the first and second rolls is maintained throughout rotation of the first and second rolls, without further means to maintain the nip. If a roll does not have a raised surface, preferably such roll has a smooth continuous surface to ensure that the nip is maintained throughout rotation of the roll. Alternatively, means can be provided to maintain the nip between irregular rolls, such as a resilient surface on one or more of the rolls, and/or a roll on a moveable axis with force continuously urging the rolls into contact with one another despite irregularities. Preferably, the first and second films are heat sealed to one another in a repeating pattern of sealed and unsealed areas.
As a second aspect, the present invention is directed to an integrated process for making an inflatable laminated article, comprising the steps of: (A) extruding a tubular film having an outside surface and en inside surface; (B) cooling the tubular film to a temperature low enough that the inside surface of the tubular film is cool enough not to adhere to itself; (C) placing the tubular film into the lay-flat configuration having a first lay-flat side and a second lay-flat side, so that a first inside lay-flat surface of the first lay-flat side of the tubular film is in contact with a second inside lay-flat surface of the second lay-flat side of the tubular film; and, (D) heating sealing selected portions of the first lay-flat side of the tubular film to the second lay-flat side of the tubular film, the heat sealing being carried out to provide a pattern of sealed and unsealed areas with the unsealed areas providing inflatable chambers between the first lay-flat side of the tubular film and the second lay-flat side of the tubular film. Depending upon the pattern of the heat sealing, the resulting heat sealed (i.e., laminated) article may or may not have to be slit along one or both side edges (i.e., slit in the machine direction) in order to provide access for means for inflating the inflatable chambers. The second aspect of the present invention is preferably otherwise carried out in accordance with preferred features set forth above in the first aspect of the present invention.
As a third aspect, the present invention is directed to an integrated process for making an inflatable laminated article, comprising the steps of: (A) extruding a flat film having a first outer surface and a second outer surface; (B) cooling the film so that the first outer surface is cool enough not to adhere to itself upon being doubled back against itself; (C) folding the film to make a crease in a machine direction of the film, with a first leaf of the film being on a first side of the crease and a second leaf of the film being on a second side of the crease, the first leaf being flat against the second leaf so that the first outer surface is doubled back against itself; and (D) heating sealing selected portions of the first leaf to the second leaf, the heat sealing being carried out to provide a pattern of sealed and unsealed areas with the unsealed areas providing inflatable chambers between the first leaf and the second leaf. The third aspect of the present invention is also preferably carried out in accordance with preferred features set forth above in the first aspect of the present invention.